1. Field of the Invention
The present invention relates to an information acquisition apparatus for acquiring information on a specimen, and more particularly to a cross section evaluating apparatus and a cross section evaluating method for evaluating the cross section of a specimen of which state and shape vary according to a change in temperature and a cross section working apparatus.
2. Related Background Art
The demand for evaluation of a cross section or formation of a fine structure in organic materials, including bio-origin materials and plastics, is increasing together with the recent increase of functional devices.
As the principal methods of preparing a cross section, utilized for obtaining information on the structure of an organic material, there are known, for example, a cutting method with a blade, an embedding method in resin, an embedding method by freezing, a breaking method by freezing, an ion etching method etc., but, in case of observing the internal structure of an organic material with an optical microscope, there is usually adopted a method of embedding the organic material in a resin and cutting it with a microtome.
However, the observation with the optical microscope is limited to a macroscopic analysis of the cross section, and, since the cut-out position cannot be designated, a large amount of work has been necessary in repeating the cross-section preparing operation, in order to achieve observation and analysis of the structure of the designated position.
For this reason, there has recently been developed an FIB-SEM apparatus in which a working function by an FIB (focused ion beam) apparatus is attached to an SEM (scanning electron microscope). The FIB apparatus irradiates a working specimen with a finely focused ion beam from an ion source, thereby achieving a working operation such as etching. The etching technology with such FIB apparatus is becoming more and more popular, and is currently widely employed for a structural analysis and a defect analysis of a semiconductor material or the like, and for preparing a specimen for a transmission electron microscope. The FIB-SEM apparatus is capable of executing a step of etching a specimen and a step of observing the cross section of the specimen by the SEM within a single apparatus, thus being capable of designating a cut-out position and observing and analyzing the structure in such designated position.
Such FIB-SEM apparatus has been proposed in various configurations. For example, the Japanese Patent Application Laid-Open No. H01-181529 proposes an apparatus capable, while the specimen is fixed, of SEM observation of the working depth in the course of FIB working and SIM (scanning ion microscope) observation of the surface of the specimen in the course of working. This apparatus is so constructed that a focused ion beam (FIB) from an FIB generation unit and an electron beam from an electron beam generation unit irradiates, with respectively different angles, a same position of the fixed specimen, and the working by the FIB and the SEM (or SIM) observation by detecting secondary electrons emitted from the specimen in response to the irradiation with the electron beam (or FIB) are alternately executed, whereby the working state of the specimen can be monitored in the course of the working process.
In addition, the Japanese Patent Application Laid-Open No. H09-274883 proposes a configuration of irradiating an electrode with a beam to prevent charging of the specimen in the course of FIB working, thereby enabling a highly precise working.